Attention has been focused on a technique for forming a transistor using a semiconductor thin film formed over a substrate having an insulating surface (also referred to as a field-effect transistor (FET) or a thin film transistor (TFT)). Such transistors are used in a wide range of electronic devices such as an integrated circuit (IC) and an image display device (display device). A semiconductor material typified by silicon is widely known as a material for a semiconductor thin film that can be used for a transistor. As another material, an oxide semiconductor has been attracting attention (e.g., Patent Document 1).
In addition, a structure in which a monitor circuit that corrects a potential of a cathode of a light-emitting element in accordance with the ambient temperature of the light-emitting element (hereinafter the ambient temperature is referred to as environmental temperature) with a transistor including an oxide semiconductor in order to correct a characteristic change due to environmental temperature of the light-emitting element provided in each pixel of an EL display device is provided outside a pixel portion is disclosed (e.g., Patent Document 2).